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Posts tagged “Spider Silk

Spider Winter Survival Tactics

Spiders are cold-blooded, or ectotherms. Their body temperature is regulated by external sources and can vary with the environment without doing them any harm. When cold weather comes spiders that overwinter as adults adapt in several ways. Their metabolism slows down and they become less active. Eventually they become dormant, entering diapause, a hibernation-like state.  At the same time, they start producing glycol and protein compounds which act as antifreeze and lower the temperature at which their cells will start freezing.  A spider has to get to at least 23 degrees F. to freeze, and sometimes considerably lower.

Where a spider spends the winter depends in large part on the species. Some seek shelter in places where temperatures remain a little warmer than outdoors, such as in leaf litter, rock piles, building cracks and under loose bark. To help block cold wind, some will even build themselves a little pod with their silk, enclosing themselves until it is warm enough to become active again.  (Photo:  spider in silk pod behind loose bark)

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Silk Rainbow

Spider Spinnerets

All spiders are capable of spinning silk, regardless of whether they use it to spin webs and trap prey or not.  Egg sacs, drag lines (so they can find their way home), drop lines (to catch them if they fall) egg cases and transportation (young spiders disperse by “ballooning” as the wind catches their silk and carries them off) are some of the other functions silk plays in the life of a spider. Silk is extruded through nozzles called spinnerets located near the tip of the abdomen. Typically a spider has two or three pairs of spinnerets.  Each one is the exterior tip of an interior silk gland and has a valve which can control the thickness and the speed with which the silk is extruded.  The different glands produce different kinds of silk used for different purposes. The spinnerets work independently for some functions, and together for others.  In the photograph, the black and yellow argiope is turning her grasshopper prey around and around as she produces a sheet of silk in which she wraps it.  Most, if not all, of the spinnerets are in use.

Spider Silk & Spinnerets

All spiders spin silk — some use it to build webs, eggs sacs, draglines, wrap prey and/or disperse in the air. Inside their bodies are glands which produce different types of silk material for different purposes.  Liquified silk proteins are pushed out spinnerets, or silk-spinning organs, located at the tip of a spider’s abdomen (most spiders have six). Once the silk solution comes in contact with the air, it solidifies.  Each spinneret has a spigot, or nozzle, which controls the consistency of the silk by forming smaller or larger strands. By winding different silk varieties together in varying proportions, spiders can form a wide range of fiber material.   Spider silk is extremely strong and flexible. Some varieties are five times as strong as an equal mass of steel and twice as strong as an equal mass of Kevlar.